With remarkable development of information technology (IT), a great variety of portable information communication devices has been popularized. As a result, in the 21st century, we are moving toward a ubiquitous society in which high-quality information service is possible regardless of time and place.
Secondary batteries are very important to realize such a ubiquitous society. Specifically, secondary batteries, which can be charged and discharged, have been widely used as an energy source for wireless mobile devices. In addition, the secondary batteries have also been used as an energy source for electric vehicles and hybrid electric vehicles, which have been proposed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuel.
As devices, to which the secondary batteries are applicable, are diversified as described above, the secondary batteries have also been diversified such that the secondary batteries can provide outputs and capacities suitable for devices to which the secondary batteries are applied. In addition, there is a strong need to reduce the size and weight of the secondary batteries.
Based on the shape of a battery case, the secondary batteries may be classified into a cylindrical battery having an electrode assembly mounted in a cylindrical metal can, a prismatic battery having an electrode assembly mounted in a prismatic metal can, and a pouch-shaped battery having an electrode assembly mounted in a pouch-shaped case made of an aluminum laminate sheet.
The electrode assembly mounted in the battery case functions as a power generating element, having a positive electrode/separator/negative electrode stack structure, which can be charged and discharged. The electrode assembly may be classified as a jelly-roll type electrode assembly configured to have a structure in which a long sheet type positive electrode and a long sheet type negative electrode, to which active materials are applied, are wound in a state in which a separator is disposed between the positive electrode and the negative electrode, or a stacked type electrode assembly configured to have a structure in which a plurality of positive electrodes having a predetermined size and a plurality of negative electrodes having a predetermined size are sequentially stacked in a state in which separators are disposed respectively between the positive electrodes and the negative electrodes.
FIG. 1 is a view showing a general structure of a pouch-shaped battery cell including a stacked type electrode assembly.
Referring to FIG. 1, a pouch-shaped battery cell 10 may be configured to have a structure in which an electrode assembly 30, including positive electrodes, negative electrodes, and separators disposed respectively between the positive electrodes and the negative electrodes, each separator being coated with a solid electrolyte, is mounted in a pouch-shaped battery case 20 in a sealed state such that two electrode leads 40 and 41 electrically connected to positive electrode and negative electrode tabs 31 and 32 of the electrode assembly 30 are exposed to the outside.
The battery case 20 includes a case body 21 having a depressed receiving part 23, in which the electrode assembly 30 is located, and a cover 22 integrally connected to the case body 21.
The battery case 20 is made of a laminate sheet including an outer resin layer 20A constituting the outermost layer of the laminate sheet, an isolation metal layer 20B for preventing penetration of materials, and an inner resin layer 20C for sealing.
The positive electrode tabs 31 and the negative electrode tabs 32 of the stacked type electrode assembly 30 are respectively coupled to the electrode leads 40 and 41 by welding. In addition, insulative films 50 are attached to the top and bottom of each of the electrode leads 40 and 41 to prevent the occurrence of a short circuit between a thermal welding device (not shown) and the electrode leads 40 and 41 and to secure sealing between the electrode leads 40 and 41 and the battery case 20 when the upper end 24 of the case body 21 and the upper end of the cover 22 are thermally welded to each other using the thermal welding device.
In recent years, however, new types of battery cells have been required in accordance with a trend change for a slim type design or various other designs. Specifically, there are needed battery cells that can be efficiently mounted even in devices which do not have a sufficient battery cell receiving space according to the reduction in size and thickness of the devices.
In addition, conventional devices were manufactured so as to have an approximately rectangular parallelepiped shape. In recent years, however, there have been developed devices having various other shapes. Battery cells having a rectangular parallelepiped shape or a cylindrical shape may not be efficiently mounted in the devices having various other shapes as described above.
For example, sides of a smartphone may be curved to improve grip. In a case in which a battery cell having the rectangular parallelepiped shape or a battery pack having the rectangular parallelepiped shape is mounted in a device designed so as to have such curved portions, however, space utilization of the device may be lowered.
That is, the curved portions of the device have dead spaces, in which the battery cell cannot be mounted. Such dead spaces lower the capacity of the device per volume.
Therefore, there is a high necessity for a battery cell configured to have a structure that is capable of reducing dead spaces in devices having various shapes such that the battery cell can be efficiently mounted in the devices while having maximized capacity.